The present invention relates to a mist supply apparatus for supplying mist which may be used for lubricating and cooling a working point or working site in a machine tool.
In general, when a work is treated by a machine tool, it is necessary to spray or eject a large amount of oil to a working site for lubrication and cooling. In this case, the oil is sprayed to a working site by means of oil conduits formed within a main spindle of a machine tool and a tool or the oil is directly sprayed to a working site without being passed through the oil conduits.
In either cases, since the liquid oil is sprayed to a working site, a large amount of oil spreads around the working site. This results in an undesired waste of oil and a serious problem of environment pollution. In general, the oil is reused by circulation and therefore it is necessary to provide an oil cooling means in a circulation path. Moreover, even though the oil is cooled, bacillus might be produced in the oil and the oil might be subjected to contamination and corrosion.
In order to solve such a problem, recently there has been proposed a minimum quantity lubrication (MQL) system, in which a small amount of oil is sprayed to a working site as an oil mist. This system has been practically used in certain applications. In a mist supply apparatus for use in the system of the kind mentioned above, oil and air are supplied to a two-fluid nozzle under compression to produce an oil mist, the thus produced oil mist is once stored in a mist chamber, and the oil mist stored in the mist chamber is supplied to a machine tool. The oil is supplied to the nozzle by means of a pump, and a given amount of the oil is supplied intermittently by driving a plunger of the pump in a reciprocal manner. A total amount of the oil supplied to the nozzle is controlled in accordance with the number of reciprocal movements of the plunger.
In known oil supply apparatuses, a mist containing both larger particles and smaller particles in combination is supplied. Therefore, when the mist is directly supplied to a working site, no problem occurs, but when the mist is supplied to a working site by means of mist conduits formed in a main spindle of a machine tool and a tool, larger mist particles are liable to be adhered onto an inner wall of the mist passage formed in the main spindle due to centrifugal force produced by a high speed rotation of the main spindle. This results in that an amount of mist actually supplied to the working site becomes smaller than a total amount of supplied mist. Then, lubrication faculty and cooling faculty of the machine tool are decreased, and working efficiency might be decreased. Furthermore, after the rotation of the main spindle is stopped, oil adhered on the inner walls of the oil conduits formed in the main spindle and tool might be dropped onto a work piece. In this manner, the work piece is stained with oil and the environment pollution might occur.
Furthermore, since a given amount of oil is supplied by the reciprocal pump in an intermittent manner, when a large amount of oil is sprayed abruptly, an excess amount of oil could not be converted into a mist, and liquid oil might be circulated. In this case, a concentration of the mist is decreased. Therefore, the known mist supply apparatus could not be effectively applied to machine tools for drilling deep holes and tapping.
In a machining center, tools are automatically exchanged and a mist is supplied to working site through mist conduits formed in a main spindle and a tool. When the known mist supply apparatus is applied to such a machining center, since mist conduits formed in tools have different diameters, a flow rate and a pressure of a mist sprayed to the working site are changed. For instance, when a tool having a mist conduit of a smaller diameter is used, although a mist pressure is increased and chips produced by cutting can be effectively removed, but a flow rate of the mist is decreased and lubricating and cooling faculties are decreased. When a tool having a mist conduit of a larger diameter is used, a flow rate of the mist is increased and sufficient lubricating and cooling faculties can be obtained, but a faculty of removing chips is decreased due to a decrease in the mist pressure.
The present invention has for its object to provide a mist supply apparatus which can overcome the above mentioned problems by supplying a mist containing mainly larger particles having a uniform size.
It is another object of the invention to provide a mist supply apparatus, in which a mist pressure can be maintained at a given value or can be increased temporarily.
It is still another object of the present invention to provide a mist supply apparatus which can supply a mist with a suitable concentration.
According to the invention, a mist supply apparatus comprising a liquid tank for containing a liquid, an atomizing means for atomizing said liquid to produce a mist of said liquid, and a transporting means for transporting said mist produced by said atomizing means to a mist supply port, wherein the apparatus further comprises a first separating means consisting of a space for containing a primary mist produced by said atomizing means and for separating larger particles in the primary mist by depositing the larger particles on an inner wall defining said space of the first separating means, and a second separating means consisting of a helical tube conduit arranged to surround said first separating means and conducting a secondary mist produced by said first separating means and for separating larger particles contained in the secondary mist by depositing the large particles on an inner wall of said tubular body of the second separating means.
According to another aspect of the invention, a mist supply apparatus comprising a liquid tank for containing a liquid, an atomizing means for atomizing said liquid from said liquid tank by means of a gas from a compressed gas supply source to produce mist of said liquid, and a mist chamber for containing said mist produced by said atomizing means, wherein a pressure control means is connected between said compressed gas supply source and set and said atomizing means for controlling a pressure within said mist chamber.
According to further aspect of the invention, a mist supply apparatus comprising a liquid tank for containing a liquid, an atomizing means for atomizing said liquid from said liquid tank by means of a gas from a compressed gas supply source to produce mist of said liquid, and a mist chamber for containing the mist produced by said atomizing means, wherein a sub-tank for containing the liquid is provided in a liquid conduit for atomizing means by means of a pump, and the liquid is continuously flowed between said sub-tank and said atomizing means.